REPORT OF THE DIRECTOR AND STATE GEOLOGIST 



kalies and a part of the Mine being assumed to go into the feld- 

 spar, the residue of alumina and lime along with the iron and 

 magnesia forming garnet, augite and hornblende. The result is 

 as follows. 



% % 



Magnetite 2.4 



Garnet 11.75 



Augite 11.0 



Anorthite 32.0 



Albite 29.7 



Orthoclase 7.5 



Quartz 5.0 



This calculation agrees well with the evidence of the thin sec- 

 tion as to the composition of the rock except that the latter 

 would indicate a somewhat larger percentage of free quartz. 

 But even 5r/ of quartz in a rock of this basicity is noteworthy, 

 and some of the rock of the hill is considerably richer in quartz 

 than that analyzed. 



A comparison of the three analyses brings out clearly the close 

 relationship of the rock to ordinary anorthosite on the one hand, 

 and its intermediate position between that and gabbro on the 

 other. But as in all gabbroic rocks there is much variation from 

 place to place and unquestionably samples from different por- 

 tions of the hill exposures would be found to vary widely. It is 

 not thought that any is more basic than that analyzed, but likely 

 much is somewhat more acid. While much of the Rand hill 

 rock is very rich in apatite it is barely present in the rock an- 

 alyzed. 



Augite-syenite 



On the east edge of Rand hill, near the top of the cliff, is a 

 small area of a greenish gray, fine grained, rather gneissoid rock 

 in which recently a quarry has been opened. This is classed 

 with rocks quite widespread in the Adirondack region and re- 

 cently described, though a small degree of doubt remains as to 

 the correctness of the reference. 1 This rock is thoroughly granu- 

 lated and gneissoid, with much recrystallization, yet, excepi for 

 its finer grain, it has precisely the same appearance and mineral 

 content as the ordinary augite-syenite as it appears at Loon lake 



'Cashing, II. P. Bui. gcol. see. Amer. 10:177-93. 



